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genirq: Provide interrupt injection mechanism

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Error injection mechanisms need a half ways safe way to inject interrupts as
invoking generic_handle_irq() or the actual device interrupt handler
directly from e.g. a debugfs write is not guaranteed to be safe.

On x86 generic_handle_irq() is unsafe due to the hardware trainwreck which
is the base of x86 interrupt delivery and affinity management.

Move the irq debugfs injection code into a separate function which can be
used by error injection code as well.

The implementation prevents at least that state is corrupted, but it cannot
close a very tiny race window on x86 which might result in a stale and not
serviced device interrupt under very unlikely circumstances.

This is explicitly for debugging and testing and not for production use or
abuse in random driver code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de
This commit is contained in:
Thomas Gleixner
2020-03-06 14:03:47 +01:00
parent da90921acc
commit acd26bcf36
6 changed files with 61 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
kernel/irq/debugfs.c
View File

@@ -190,39 +190,7 @@ static ssize_t irq_debug_write(struct file *file, const char __user *user_buf,
return -EFAULT;
if (!strncmp(buf, "trigger", size)) {
unsigned long flags;
int err;
/* Try the HW interface first */
err = irq_set_irqchip_state(irq_desc_get_irq(desc),
IRQCHIP_STATE_PENDING, true);
if (!err)
return count;
/*
* Otherwise, try to inject via the resend interface,
* which may or may not succeed.
*/
chip_bus_lock(desc);
raw_spin_lock_irqsave(&desc->lock, flags);
/*
* Don't allow injection when the interrupt is:
* - Level or NMI type
* - not activated
* - replaying already
*/
if (irq_settings_is_level(desc) ||
!irqd_is_activated(&desc->irq_data) ||
(desc->istate & (IRQS_NMI | IRQS_REPLAY))) {
err = -EINVAL;
} else {
desc->istate |= IRQS_PENDING;
err = check_irq_resend(desc);
}
raw_spin_unlock_irqrestore(&desc->lock, flags);
chip_bus_sync_unlock(desc);
int err = irq_inject_interrupt(irq_desc_get_irq(desc));
return err ? err : count;
}